# Chem 2425

30 Questions  I  By Ochiengj

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 1 3. Water has a specific heat of 4.18 J/g · 0C. If 35.0 g of water at 98.8 0C loses 4.94 kJ of heat, what is the final temperature of the water?
 A. 32.00C
 B. 46.20C
 C. 47.20C
 D. 57.20C
 E. 65.0C
2.  21. For the second-order reaction below, the rate constant of the reaction is 9.4 × 10–3 M–1s–1. How long (in seconds) is required to decrease the concentration of A from 2.16 M to 0.40 M?
 2A → B rate = k[A]2

 A. 2.0 × 10^1 s
 B. 7.8 × 10^1 s
 C. 1.8 × 10^2 s
 D. 1.9 × 10^2 s
 E. 2.2 × 10^2 s
3.  Calcium carbonate decomposes to calcium oxide and carbon dioxide.
 CaCO3(s)   CaO(s) + CO2(g) ΔH0 = 179 kJ
The equilibrium constant for this reaction is 9.7 × 1024 at 298 K. What is the equilibrium constant at 575 K? (R = 8.31 J/mol·K)
 A. 7.5 × 10^-16
 B. 1.3 × 10^-8
 C. 1.4 × 10^-38
 D. 1.3 × 10^-15
 E. 1.0 * 10^-23
 4 What is the correct equilibrium constant expression for the following reaction?         CO2(g) + 2H2O(g)  CH4(g) + 2O2(g) a.                  b.                  c.              d.
 A. A
 B. B
 C. C
 D. D
 5 14. Dinitrogen pentaoxide decomposes to nitrogen dioxide and oxygen according to the following balanced chemical equation and rate expression.         2N2O5(g) → 4NO2(g) + O2(g)         rate = k[N2O5] What is the overall reaction order?
 A. 0
 B. 1
 C. 2
 D. 5
 E. 7
6.  16. The initial rates method was used to study the reaction below.         2A + B + C → D + E
 [A] (mol/L) [B] (mol/L) [C] (mol/L) Δ[D]/Δt (mol/L·s) 0.150 0.250 0.300 1.47 × 106 0.150 0.125 0.300 3.68 × 107 0.150 0.250 0.600 2.94 × 106 0.300 0.125 0.300 7.35 × 107

 A. Rate = 8.71 × 104[A]2 × [B] × [C]
 B. Rate = 5.23 × 104[A] × [B]2 × [C]
 C. Rate = 2.90 × 103[A]2 × [B] × [C]2
 D. Rate = 8.71 × 104[A] × [B] × [C]2
 7 . Nitrosyl chloride decomposes according to the chemical equation below.         2NOCl(g)  2NO(g) + Cl2(g) A pressure of 0.320 atm of nitrosyl chloride is sealed in a flask and allowed to reach equilibrium. If 22.6% of the NOCl decomposes, what is the equilibrium constant for the reaction?
 A. 0.00153
 B. 0.00308
 C. 0.00611
 D. 0.0073
 E. 0.02471
 8 4. When 66.0 g of an unknown metal at 28.50C is placed in 83.0 g H2O at 78.50C, the water temperature decreases to 75.90C. What is the specific heat capacity of the metal? The specific heat capacity of water is 4.184 J/g0C.
 A. 0.055 J/g· 0C
 B. 0.29 J/g · 0C
 C. 0.69 J/g · 0C
 D. 0.18 J/g · 0C
 E. 2.6 J/g · 0C
 9 6. When 10.0 g KOH is dissolved in 100.0 g of water in a coffee-cup calorimeter, the temperature rises from 25.18 0C to 47.53 0C. What is the enthalpy change per gram of KOH dissolved in the water? Assume that the solution has a specific heat capacity of 4.18 J/g0C.
 A. –116 J/g
 B. –934 J/g
 C. –1.03 × 103 J/g
 D. –2.19 × 103 J/g
 E. –1.03 × 104 J/g
 10 7. 10.0 g of ice at 0.00 0C is mixed with 25.0 g of water at 35.000C in a coffee-cup calorimeter. What is the final temperature of the mixture? The specific heat of water is 4.18 J/g 0C; the heat of fusion of water is 333 J/g.
 A. 0.00 0C
 B. 2.24 0C
 C. 5.22 0C
 D. 25.0 0C
 E. 47.8 0C
 11 28. For the system         CO(g) + H2O(g)  CO2(g) + H2(g) K is 1.6 at 900 K. If 0.400 atm CO(g) and 0.400 atm H2O(g) are combined in a sealed flask, what is the equilibrium partial pressure of CO2(g)?
 A. 0.22 atm
 B. 0.31 atm
 C. 0.47 atm
 D. 0.47 atm
 E. 0.65 atm
 12 12. The rate of reaction for the formation of carbon monoxide is measured at 1.24 mol/L·hr. What is the rate of formation of carbon monoxide in units of mol/L·s?         CH3CHO(g) → CH4(g) + CO(g)
 A. 3.44 × 10-4 mol/L·s
 B. 2.07 × 102 mol/L·s
 C. 1.24 mol/L·s
 D. 74.4 mol/L·s
 E. 4.64 × 103 mol/L·s
 13 19. The reaction A → B follows first-order kinetics with a half-life of 21.7 hours. If the concentration of A is 0.023 M after 48.0 hours, what is the initial concentration of A?
 A. 0.0050 M
 B. 0.051 M
 C. 0.51 M
 D. 0.11 M
 E. 2.0 × 102 M
 14 29. Which of the following may change the ratio of products to reactants in an equilibrium mixture for a chemical reaction involving gaseous species?     1.    Increasing the temperature.     2.    Adding a catalyst.     3.    Adding gaseous reactants.
 A. 1 only
 B. 2 only
 C. 3 only
 D. 1 and 2
 E. 1 and 3
15.  20. For the first-order reaction below, the concentration of product B after 24.2 seconds is 0.322 M. If k = 8.75 × 10-2 s-1, what was the initial concentration of A?
 A → 2B rate = k[A]
 A. 0.0341 M
 B. 0.183 M
 C. 1.34 M
 D. 2.68 M
 E. 29.3 M
 16 1. If 50.0 g of benzene, C6H6, at 25.00C absorbs 2.71 kJ of energy in the form of heat, what is the final temperature of the benzene? The specific heat of benzene is 1.72 J/g·0C.
 A. 25.00C
 B. 31.50C
 C. 56.50C
 D. 32.30C
 E. 57.30C
17.  Use the equilibrium constants for the following reactions at 700 0C
 2SO2(g) + O2(g)  2SO3(g) K1 = 4.8 2NO(g) + O2(g)  2NO2(g) K2 = 16
to determine the equilibrium constant for the following reaction.         SO3(g) + NO(g)  SO2(g) + NO2(g)
 A. 0.3
 B. 0.55
 C. 0.85
 D. 1.8
 E. 3.3
 18 Which of the following statements is/are CORRECT?     1.    Product concentrations appear in the numerator of an equilibrium constant expression.     2.    A reaction favors the formation of products if K >> 1.     3.    Stoichiometric coefficients are used as exponents in an equilibrium constant expression.
 A. 1 only
 B. 2 only
 C. 3 only
 D. 2 and 3
 E. 1, 2, and 3
 19 13. For the reaction below, if the rate of appearance of Br2 is 0.180 mol/L·s, what is the rate of disappearance of NOBr?         2NOBr(g) → 2NO(g) + Br2(g)
 A. –0.360 mol/L·s
 B. –0.090 mol/L·s
 C. 0.090 mol/L·s
 D. 0.180 mol/L·s
 E. 0.360 mol/L·s
 20 17. The rate constant of a first-order decomposition reaction is 0.0147 s–1. If the initial concentration of reactant is 0.178 M, what is the concentration of reactant after 30.0 seconds?
 A. 8.72 × 105 M
 B. 0.0645 M
 C. 0.115 M
 D. 0.0785 M
 E. 0.643 M
 21 2. If 495 J is required to change the temperature of 12.7 g of sodium chloride from 75.00C to 135 0C, what is the specific heat of sodium chloride?
 A. 0.866 J/g·0C
 B. 2.60 J/g·0C
 C. 0.650 J/g·0C
 D. 1.15 J/g·0C
 E. 2.83 × 105 J/g·0C
 22 The initial rates method was used to study the reaction below.         A + 3B =2C     [A] (mol/L)    [B] (mol/L)   -D[A]/Dt (mol/L×s)     0.210        0.150         3.41 x 10^3     0.210        0.300        1.36 x 10^2     0.420        0.300        2.73 x 10^-2
 A. Rate = 0.515[A] x [B]
 B. Rate = 0.515[A]^2 x [B]
 C. Rate = 0.721[A]^2 x [B]
 D. Rate = 0.721[A] x [B]^2
 E. Rate = 0.721[A]^2 x [B]^2
 23 8. All of the following statements are true EXCEPT
 A. Hess' law states that ΔH for an overall reaction is the sum of the ΔH values for the individual equations.
 B. The molar enthalpy of formation of a compound is equal to the enthalpy change when one mole of the compound is formed from elements.
 C. A reaction with a negative enthalpy is exothermic.
 D. The enthalpy of formation of an element in its most stable state is equal to zero.
 E. The sum of the enthalpies of formation of the products in a chemical reaction is defined as the enthalpy of reaction.
 24 25. Write a balanced chemical equation which corresponds to the following equilibrium constant expression.
 A. 1/2N2(g) + 3/2H2(g) = NH3(g)
 B. N2(g) + 3 H2(g) = 2NH3(g)
 C. 2NH3(g) = N2(g) + 3H2(g)
 D. NH3(g) = 1/2N2(g) + 3/2H2(g)
 E. 2N2(g) + 6H2(g) = 4NH3(g)
 25 11. For the reaction below relate the rate of disappearance of hydrogen to the rate of formation of ammonia.         N2(g) + 3H2(g) → 2NH3(g)
 A. A: +
 B. B: 3
 C. C: 1/2
 D. D: -1/3
 E. E: -
 26 9. Determine the heat of reaction for the combustion of ammonia,         4NH3(g) + 7O2(g) → 4NO2(g) + 6H2O(l) using molar enthalpies of formation. NH3(g)    –45.9 NO2(g)    +33.1 H2O(l)    –285.8
 A. +30.24 kJ
 B. –206.9 kJ
 C. –298.6 kJ
 D. –1398.8 kJ
 E. –1663.6 kJ
 27 10. The standard molar enthalpy of formation of NH3(g) is –45.9 kJ/mol. What is the enthalpy change if 9.51 g N2(g) and 1.96 g H2(g) react to produce NH3(g)?
 A. –10.3 kJ
 B. –20.7 kJ
 C. –29.8 kJ
 D. –43.7 kJ
 E. –65.6 kJ
 28 18. The rate constant for the decomposition of cyclobutane is 2.08 × 10-2 s-1 at high temperatures.         C4H8(g) → 2C2H4(g) How many seconds are required for an initial concentration of 0.100 M C4H8(g) to decrease to 0.0450 M?
 A. 0.00114 s
 B. 1.07 s
 C. 2.64 s
 D. 38.4 s
 E. 874 s
29.  22. For the first-order reaction below, the initial concentration of A is 0.80 M. What is the half-life of the reaction if the concentration of A decreases to 0.10 M in 54 seconds?
 A → B rate = k[A]

 A. 18 s
 B. 24 s
 C. 36 s
 D. 48 s
 E. 51 s
 30 5. A coffee-cup calorimeter contains 10.0 g of water at 59.000C. If 3.00 g gold at 15.20 0C is placed in the calorimeter, what is the final temperature of the water in the calorimeter? The specific heat of water is 4.18 J/g ·0C; the specific heat of gold is 0.128 J/g ·0C.
 A. 55.37 C
 B. 58.60 C
 C. 59.40 C
 D. 60.80 C
 E. 64.19 C
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